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Transforming growth factor beta-1 and gene polymorphisms in oriental ankylosing spondylitis
H S Howe1, P L Cheung, K O Kong
1Department of Rheumatology, Allergy and Immunology, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore 308433. Hwee_Siew_Howe@ttsh.com.sg
Objectives:
To study serum levels of transforming growth factor beta-1 (TGFbeta1) and the expression of TGFbeta1 in in vitro peripheral blood mononuclear cell (PBMC) cultures in oriental ankylosing spondylitis (AS) patients, and to determine their association with codon 10 and 25 TGFB1 gene polymorphisms.
Methods:
Serum levels of TGFbeta1 were measured by enzyme-linked immunosorbent assay (ELISA). The ability of PBMCs to synthesize TGFbeta1 and other cytokines was assessed by in vitro cultures stimulated with mitogen. Genomic DNA was extracted from PBMCs of AS patients (n=72) or unrelated healthy controls (n=96). The codon 10 and 25 polymorphisms in the TGFB1 gene were analysed using standard polymerase chain reaction-based methods.
Results:
AS patients had significantly higher serum TGFbeta1 levels than controls (P<0.001). There was no difference in the distribution of codon 10 and 25 TGFB1 genotypes between AS patients and controls. Incubation of AS and control PBMC with phytohaemagglutinin (PHA) led to upregulation of TGFbeta1, interleukin-10, tumour necrosis factor-alpha (TNFalpha) and interferon-gamma (IFNgamma) assessed by ELISA. Importantly, PHA-induced TGFbeta1 production was significantly enhanced in AS patients compared with normal controls whereas the production of the pro-inflammatory cytokines TNFalpha and IFNgamma was reduced.
Conclusions:
Our results show that AS patients express significantly higher levels of serum TGFbeta1 independent of the codon 10 and 25 genotype. Activation of AS PBMCs led to enhanced TGFbeta1 production accompanied by reduction of TNFalpha and IFNgamma while the converse was observed in normal controls.